System, method, and apparatus for measuring golf club deformation

ABSTRACT

Provided is a system for measuring golf club deformation that can easily measure golf club deformation during a golfer&#39;s golf swing as usual. A measurement system ( 1 ) according to the present invention is provided with an image pickup apparatus ( 4 ), attached to a golf club ( 3 ) and facing a direction that includes at least one identifier attached to the golf club ( 3 ) for specification of a position on the golf club ( 3 ), and with a measurement apparatus ( 2 ) that measures the golf club deformation based on position information of the at least one identifier, the position information being acquired from an image of the golf club captured by the image pickup apparatus ( 4 ) during a swing.

TECHNICAL FIELD

The present invention relates to a system, a method, and an apparatus for measuring golf club deformation during a golf swing.

BACKGROUND ART

In general, when a golfer swings a golf club and hits a golf ball (takes a shot) while intending for the ball to fly straight, the direction in which the golf ball flies is ideally relatively straight, without curving (or only curving slightly). In particular, by using an appropriate golf club, golfers can make such an ideal shot relatively easily. It is not easy, however, for a golfer to actually visit a store and select a golf club that is a good match.

The flight direction of the ball is affected by factors such as the amount of backspin, the launch angle, and the like in the golf swing. These factors are known to be greatly affected by, for example, movement of the golf club head (referred to below simply as “head”) when the head hits (impacts) the golf ball. Furthermore, during the golfer's golf swing, the shaft of the golf club deforms in response to the weight of the golf club head and the force applied to the golf club by the golfer. Deformation in which the golf club shaft flexes is typically referred to as “flex”. Flex is considered to exert an extremely large influence over whether a golfer can execute an ideal golf swing.

Conventionally, a method has therefore been proposed to measure strain on the shaft during the golf swing by attaching a strain gauge to the golf club (for example, see Non-Patent Literature 1). With the method disclosed in Non-Patent Literature 1, a strain gauge is attached to the surface of the golf club shaft, and the flex produced in the shaft during the golf swing can be measured.

Furthermore, in order to measure the shape of a shaft that deforms during the golfer's golf swing, a method has conventionally been proposed to film a golf swing, using a golf club with a number of markers attached thereto, with a plurality of image pickup apparatuses and to measure the 3D coordinates of the markers by motion capture (for example, see Patent Literature 1). With the system disclosed in Patent Literature 1, the shape of the shaft during the golf swing can be visualized by curve approximation from the measured 3D coordinates.

CITATION LIST

Non-Patent Literature 1: NARUO Takeshi et al., “Research on golf shaft flex”, Proceedings of the Joint Symposium: Symposium on Sports Engineering and Symposium on Human Dynamics, The Japan Society of Mechanical Engineers, 1995, No. 95-45

Patent Literature 1: JP2011-183090A

SUMMARY OF INVENTION

With the method recited in Non-Patent Literature 1, however, since information on the overall flex of the golf club is acquired, it becomes necessary to attach a number of strain gauges to the shaft. In this case, the amount of wiring for the strain gauges increases, making it difficult for the golfer to execute a golf swing as usual.

On the other hand, with the method disclosed in Patent Literature 1, it is necessary to adjust the relative positions of the image pickup apparatuses in order to acquire the 3D position coordinates of the markers. As the number of image pickup apparatuses increases, the adjustment of course requires more time, making it difficult to measure golf club deformation.

Hence, with the conventional method and system, the golf club deformation during a golf swing cannot be easily measured for the golfer's golf swing as usual.

The present invention has been conceived in light of these circumstances, and it is an object thereof to provide a system, a method, and an apparatus for measuring golf club deformation that can easily measure golf club deformation for a golfer's golf swing as usual.

In order to achieve the above object, a system for measuring golf club deformation according to the present invention is a system for measuring golf club deformation during a swing of a golf club by a golfer, including: an image pickup apparatus attached to the golf club and facing a direction that includes at least one identifier attached to the golf club for specification of a position on the golf club; and a measurement apparatus configured to measure the golf club deformation based on position information of the at least one identifier, the position information being acquired from an image of the golf club captured by the image pickup apparatus during the swing.

According to the system for measuring golf club deformation of the present invention, it is possible easily to measure golf club deformation during a golfer's golf swing as usual.

In the system according to the present invention, the measurement apparatus preferably includes: an image acquisition unit configured to acquire the image of the golf club during the swing from the image pickup apparatus; a position information acquisition unit configured to recognize the at least one identifier in the acquired image and to acquire position information of the recognized at least one identifier; and a measurement unit configured to measure the golf club deformation based on the acquired position information.

According to this structure, it is possible to measure the golf club deformation during a golf swing easily with the functional units included in the measurement apparatus.

In the system according to the present invention, the at least one identifier is preferably provided on a head of the golf club.

According to this structure, it is possible to measure movement of the golf club head and/or flex of the shaft reflected in movement of the head.

In the system according to the present invention, the golf club deformation is preferably at least one of movement of a head and flex of a shaft of the golf club, so that one or both of the behavior of the head and the flex of the shaft of the golf club can be measured.

In the system according to the present invention, the image pickup apparatus preferably weighs less than 90 g.

According to this structure, since the head speed is not dramatically reduced during the swing, it is possible to measure golf club deformation in which the effect of the head speed as usual is reflected.

In order to achieve the above object, a method for measuring golf club deformation according to the present invention is a method for measuring golf club deformation during a swing of a golf club by a golfer, including the steps of: capturing an image of the golf club with an image pickup apparatus during a golf swing using the golf club, the golf club including at least one identifier for specification of a position on the golf club and having the image pickup apparatus attached thereto facing a direction that includes the at least one identifier; acquiring the image of the golf club during the swing from the image pickup apparatus; recognizing the at least one identifier in the image captured by the image pickup apparatus and acquiring position information of the recognized at least one identifier; and determining the golf club deformation based on the acquired position information.

According to the method for measuring golf club deformation of the present invention, it is possible easily to measure golf club deformation during a golfer's golf swing as usual.

In order to achieve the above object, an apparatus for measuring golf club deformation according to the present invention is an apparatus for measuring golf club deformation during a swing of a golf club by a golfer, wherein the apparatus measures the golf club deformation based on position information of at least one identifier attached to the golf club for specification of a position on the golf club, the position information being acquired from an image of the golf club captured during the swing by an image pickup apparatus attached to the golf club and facing a direction that includes the at least one identifier.

According to the apparatus for measuring golf club deformation of the present invention, it is possible easily to measure golf club deformation during a golfer's golf swing as usual.

According to the present invention, it is possible easily to measure golf club deformation during a golfer's golf swing as usual by performing predetermined measurements based on images of the golf swing acquired by an image pickup apparatus attached to the golf club facing a direction that includes at least one identifier attached to the golf club.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be further described below with reference to the accompanying drawings, wherein:

FIG. 1 illustrates a system for measuring golf club deformation according to an embodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for measuring golf club deformation according to an embodiment of the present invention;

FIG. 3 illustrates the relationship between a projection plane of the image pickup apparatus in FIG. 1 and the head and shaft of the golf club;

FIG. 4 is a graph illustrating an example of a golf club image captured during a golf swing by the image pickup apparatus in FIG. 1;

FIG. 5 illustrates an example of the change in position of each marker over time in the X-axis direction on the projection plane of the image pickup apparatus;

FIG. 6 illustrates an example of the change in position of each marker over time in the Y-axis direction on the projection plane of the image pickup apparatus;

FIG. 7 illustrates an example of the trajectory on the projection plane of the marker on the head during a golf swing;

FIG. 8 illustrates an example of the change in relative angle of the head over time during the golf swing relative to the initial position of the head;

FIG. 9A illustrates an example of the trajectory on the projection plane of the marker on the head during a golf swing;

FIG. 9B illustrates an example of the trajectory on the projection plane of the marker on the head during a golf swing;

FIG. 9C illustrates an example of the trajectory on the projection plane of the marker on the head during a golf swing;

FIG. 10A illustrates an example of the change in relative angle of the head over time during a golf swing relative to the initial position of the head;

FIG. 10B illustrates an example of the change in relative angle of the head over time during a golf swing relative to the initial position of the head; and

FIG. 10C illustrates an example of the change in relative angle of the head over time during a golf swing relative to the initial position of the head.

DESCRIPTION OF EMBODIMENTS

With reference to the drawings, the following describes a system, a method, and an apparatus for measuring golf club deformation according to embodiments of the present invention.

FIG. 1 illustrates a measurement system 1 for measuring golf club deformation according to an embodiment of the present invention. The measurement system 1 for measuring golf club deformation in FIG. 1 is provided with a measurement apparatus 2 and an image pickup apparatus 4 attached to a golf club 3. Like an ordinary golf club, the golf club 3 is provided with a shaft 5, a head 6, and a grip 7.

The image pickup apparatus 4 is attached to the shaft 5 of the golf club 3 facing a direction that includes an identifier, described below, and preferably so that the optical axis is substantially parallel to the shaft axis of the shaft 5. The position of attachment of the image pickup apparatus 4 on the shaft 5 is, for example, directly below or near the grip 7 (directly below in the example in the figures) at a position at which a golfer 8 can execute a golf swing as usual. Attaching the image pickup apparatus 4 to such a position yields the advantages of the position of the image pickup apparatus 4 being affected little by deformation of the golf club 3 during the golf swing and the ability to acquire images of the golf club 3 over a wide range. Even when the optical axis of the image pickup apparatus 4 is not parallel to the shaft axis, any range in which the identifier of the head 6 (not illustrated) can be imaged throughout the golf swing is acceptable.

The image pickup apparatus 4 is, for example, configured using a digital high-speed camera or a wireless camera. The frame rate of the camera is 30 frames per second (fps) or less for a wireless camera and is over 30 fps for a digital high-speed camera. The image pickup apparatus 4 is light enough for the golfer 8 to execute a golf swing as usual with the golf club 3. Specifically, the weight of the image pickup apparatus 4 is preferably less than 90 g. The image pickup apparatus 4 more preferably weighs 60 g or less.

As is clear from Table 1, if the weight of the image pickup apparatus 4 is 90 g or more, the head speed decreases dramatically, whereas if the image pickup apparatus 4 weighs 60 g or less, there is almost no effect on the head speed. If the speed reduction rate is less than the speed reduction rate when the image pickup apparatus 4 weighs 90 g, the image pickup apparatus 4 is highly usable for actual measurement. Therefore, it is possible to measure golf club deformation in conditions closer to actual conditions, with the effect of the head speed being reflected. Note that the weight of the image pickup apparatus 4 is considered here to include the weight of the camera body and the camera lens constituting the image pickup apparatus 4, and of the member for attaching the image pickup apparatus 4 to the shaft 5.

TABLE 1 Image pickup apparatus No image pickup weight (g) apparatus (0 g) 30 60 90 Head Golfer A 45.1 45.2 45.0 43.8 speed Golfer B 42.1 42.1 42.2 41.4 (m/s) Golfer C 43.4 43.2 43.1 42.5 Golfer D 47.1 47.0 46.9 46.3 Golfer average 44.4 44.4 44.3 43.5

While not shown in FIG. 1, when the image pickup apparatus 4 is configured with a device other than a wireless camera, wiring may be provided between the image pickup apparatus 4 and the measurement apparatus 2 in a manner that does not impede the golf swing by the golfer 8. Note that even when the image pickup apparatus 4 is configured with a device other than a wireless camera, it is not necessary to provide wiring if a removable storage medium can be stored in the image pickup apparatus 4.

At least one identifier (not illustrated) for specification of a position on the golf club is attached to the golf club 3. The identifier refers to a characteristic that is distinguishable from other portions during image processing and may, for example, be a logo or characters applied to a commercial golf club head or the markers M1 to M3 described in detail with reference to FIG. 4. The identifier is, for example, applied to the golf club 3 using reflective tape, paint, or the like. Another material may also be used for the identifier as long as the material yields at least a predetermined amount of contrast with surrounding pixels during image processing.

The measurement apparatus 2 is, for example, configured using a personal computer or the like provided with a central processing unit (CPU) and includes an image acquisition unit, a position information acquisition unit, and a measurement unit (not illustrated). Furthermore, the measurement apparatus 2 may be provided with a display unit and be configured to display the results of measuring golf club deformation on the display unit. The functions of the image acquisition unit, position information acquisition unit, and measurement unit are described below with reference to FIG. 2.

When the golfer 8 executes a golf swing to hit a golf ball 9 with the golf club 3, the measurement system 1 executes measurement processing with the measurement apparatus 2 on images captured by the image pickup apparatus 4 and measures the golf club deformation during the golf swing by the golfer 8. With reference to FIG. 2, the following describes the method for measurement employed in the measurement system 1 in greater detail.

FIG. 2 is a flowchart illustrating a method for measuring golf club deformation according to an embodiment of the present invention. First, the image pickup apparatus 4 captures images of the golf club during a golf swing (step S01). Subsequently, with the image acquisition unit, the measurement apparatus 2 acquires images of the golf club, such as images of the head 6, during the golf swing from the image pickup apparatus 4 (step S02). These images of the golf club may be video data, in any format, captured by the image pickup apparatus 4.

With the position information acquisition unit, the measurement apparatus 2 then extracts any image data from the video data captured by the image pickup apparatus 4 in step S01, and for the extracted image data, recognizes the identifier on the head 6 and acquires position information of the recognized identifier (step S03). For example, when the identifiers are circles indicated by markers M1 to M3 in FIG. 4, the position information acquisition unit extracts each identifier using a circle fitting method and acquires the coordinates of the center position as the position information.

The coordinates are, for example, the coordinates in a virtual projection plane 10 of the image pickup apparatus 4, described below with reference to FIGS. 3 and 4.

Via the measurement unit, the measurement apparatus 2 measures the golf club deformation based on the position information acquired in step S03 (step S04). Specifically, the measurement unit can measure at least one of movement of the head 6 and flex of the shaft 5. Furthermore, the measurement unit may measure both the movement of the head 6 and the flex of the shaft 5 based on the position of the head 6 with respect to the image pickup apparatus 4. In this case, as the position of the head 6, the measurement unit measures the position on the projection plane 10 of the image pickup apparatus 4. Furthermore, the measurement unit can determine the change in position of the head 6 over time on the projection plane 10 and measure the change in status of the movement of the head 6 and the flex of the shaft 5 during the golf swing. Below, with reference to FIGS. 3 and 4, the above steps S03 and S04 are described in greater detail by describing the projection plane 10 of the image pickup apparatus 4.

FIG. 3 illustrates the relationship between the virtual projection plane 10 of the image pickup apparatus 4 in FIG. 1 and the head 6 and shaft 5 of the golf club 3 in FIG. 1. The projection plane 10 is a plane perpendicular to the optical axis of the image pickup apparatus 4. The image pickup apparatus 4 is attached to the shaft 5 via an attachment member 11, and the portion of the shaft 5 where the image pickup apparatus 4 is attached either substantially has no flex or has less flex than the head 6 and the portion of the shaft 5 near the head 6. When the optical axis of the image pickup apparatus 4 and the shaft axis are parallel, the shaft axis of the shaft 5 in a state without flex is perpendicular to the projection plane 10.

When flex is produced in the shaft 5 during a golf swing to yield a state such as that of shafts 5 a and 5 b shown with dashed lines, the shaft axis is not perpendicular to the projection plane 10. The position coordinates on the projection plane 10 of the markers M1 to M3 on the head 6 are represented as pixel positions corresponding to the coordinate values along the X-axis and Y-axis depicted to the lower left in FIG. 3. The Z-axis is an axis parallel to the optical axis of the image pickup apparatus 4. Note that for the sake of clarity, the illustration of the flex of the shafts 5 a and 5 b is exaggerated. Actually occurring flex is often less than the flex in FIG. 3.

FIG. 4 is a graph illustrating an example of a golf club image captured during a golf swing by the image pickup apparatus 4 in FIG. 1. The position of the shaft 5 and the head 6 in FIG. 4 is the position immediately before impact, which is the point in time at which the head 6 hits the golf ball 9. The markers M1 to M3, which are identifiers, are attached to the upper surface of the head 6. At least one identifier suffices, and of course it is also possible to provide three markers, as in the figures, or to provide a plurality of markers of differing types. In FIG. 4, the markers M4 to M6 shown with dashed lines respectively correspond to the positions of the markers M1 to M3 at the start of the golf swing. In step S03 above, the position information acquisition unit of the measurement apparatus 2 acquires the position information of the markers M1 to M3 as pixel coordinates, taking the origin (0, 0) to be the lower-left in the XY plane that is the projection plane. The position information of the markers M1 to M3 on the projection plane 10 is the relative position of the head 6 with respect to the image pickup apparatus 4.

In step S04 above, the measurement unit of the measurement apparatus 2 can measure the flex of the shaft 5 reflected in the relative position of the head 6 with respect to the image pickup apparatus 4. Furthermore, using the golf club 3 in which any number of markers are attached to the shaft 5, similar measurement can be performed to measure the flex amount or flex form of the shaft 5 in even greater detail.

With regard to the movement of the head 6, the measurement unit can, for example, measure the rotation behavior of the head 6 by calculating the angle formed between a line connecting the markers M4 and M5 (referred to below as the M4-M5 line), corresponding to the face orientation of the head 6 at the start of the golf swing, and a line connecting M1 and M2 (referred to below as the M1-M2 line). In this way, the rotation behavior of the head 6 can be measured as the relative angle, at each point in time during the golf swing, with respect to the face orientation of the head 6 at the start of the golf swing. Furthermore, using a predetermined model, it is also possible to calculate torsion of the shaft from the rotation behavior of the head.

Below, with reference to FIGS. 5 through 8, step S04 above is described in greater detail. As illustrated in FIG. 5, the measurement unit of the measurement apparatus 2 can determine the change over time in position information on the projection plane 10 of the markers M1 to M3 acquired by the position information acquisition unit. FIG. 5 illustrates the change in position of the markers M1 to M3 over time in the X-axis direction on the projection plane 10 of the image pickup apparatus 4. The horizontal axis represents time (ms), and the vertical axis represents the position (pixels) of each marker in the X-axis direction on the projection plane 10 of the image pickup apparatus. The point at a time (ms) of 0 is the time of impact, when the head 6 hits the golf ball 9. In FIG. 5, it is clear that the X-axis direction position on the projection plane of the markers M1 to M3 on the head 6 tends to move left and right similarly towards the time of impact. To explain this tendency in greater detail, the markers M1 to M3 on the head 6 first move to the left along the X-axis on the projection plane 10 immediately after the start of the golf swing, and subsequently move slowly to the right along the X-axis on the projection plane 10, moving once again to the left along the X-axis on the projection plane 10 immediately before impact, until reaching the time of impact.

FIG. 6 illustrates the change in position of the markers M1 to M3 over time in the Y-axis direction on the projection plane of the image pickup apparatus 4. The horizontal axis represents time (ms), and the vertical axis represents the position (pixels) of each marker in the Y-axis direction on the projection plane 10 of the image pickup apparatus. As in FIG. 5, the point at a time (ms) of 0 is the time of impact, when the head 6 hits the golf ball 9. In FIG. 6, it is clear that the Y-axis direction position on the projection plane of the markers M1 to M3 on the head 6 tends to move up and down similarly towards the time of impact. To explain this tendency in greater detail, the markers M1 to M3 on the head 6 first sway up and down in the Y-axis direction on the projection plane 10 immediately after the start of the golf swing and then move suddenly in the direction of the Y-axis. Next, the markers M1 to M3 lower gradually up to a certain point and then lowers suddenly towards impact.

As illustrated in FIGS. 5 and 6, according to the present embodiment, it is possible to measure deformation of the golf club 3 reflected in movement of the head 6. Furthermore, according to the present embodiment, it is possible to acquire information on the trajectory on the projection plane 10 of the marker M1 on the head 6 during the golf swing, as illustrated in FIG. 7. The diamond on the plot in FIG. 7 indicates impact. The trajectory of the marker M1 on the projection plane 10 of the image pickup apparatus 4 indicates how much the head 6 is displaced relative to the image pickup apparatus 4. Within the deformation of the golf club 3, the factor contributing most to the relative displacement of the head 6 relative to the image pickup apparatus 4 is considered to be the flex of the shaft 5. Accordingly, from the trajectory of the marker M1 as illustrated in FIG. 7, the flex of the shaft 5 at the time of the golf swing can be measured.

Furthermore, the rotation behavior of the head can be measured as illustrated in FIG. 8. This rotation behavior includes, for example, rotation in the toe down direction, i.e. the direction in which the head 6 moves away from the shaft axis, and rotation in the striking direction with the shaft as the axis. In FIG. 8, the vertical axis represents the relative angle, and the horizontal axis represents time (ms). The relative angle indicates the angles of the M1-M2 line and M1-M3 line during the golf swing with respect to the M4-M5 line, corresponding to the M1-M2 line, and the M4-M6 line, corresponding to the M1-M3 line, at the start of the golf swing. A positive value indicates a rotation angle in the striking direction, and a negative value indicates a rotation angle in the opposite direction. The solid line represents the change over time in the angle of the M1-M2 line of the head 6 with respect to the M4-M5 line. The dashed line represents the change over time in the angle of the M1-M3 line with respect to the M4-M6 line. From FIG. 8, it is clear that immediately after the start of the golf swing, the face surface exhibits a positive rotation angle due to inertia, yet subsequently becomes negative, with the face surface gradually rotating in the positive direction towards impact.

In FIG. 8, the change in the solid line is greater than the change in the dashed line. This is considered to be because the head 6 during the golf swing moves in the so-called toe down direction (the direction in which the head 6 moves away from the shaft axis), producing flex in the shaft 5. By further analyzing such data together with the measurement results for shaft flex as described above, it is considered possible to analyze the correlation between shaft flex and head movement.

In this way, according to the method of the present embodiment, it is possible to measure movement of the head 6 during a golf swing by the golfer 8 easily without needing to use a plurality of image pickup apparatuses for measuring golf club deformation. Note that in FIGS. 5, 6, and 8, the data on head movement and shaft flex during the golf swing are illustrated as temporal data, yet these data are not acquirable only as temporal data. For example, it is of course possible to calculate these data for any point in time of interest, such as the time of impact. In this case, deformation of the golf club 3 can be determined as an amount of displacement from the state in which the golf club 3 undergoes no deformation whatsoever.

Next, the results of applying the system and method for measurement of the present embodiment to a plurality of subjects are described with reference to FIGS. 9 and 10. Like FIG. 7, the measurement results in FIGS. 9A to 9C illustrate the trajectory on the projection plane 10 of the marker M1 on the head 6 during a golf swing. Like FIG. 8, the measurements results in FIGS. 10A to 10C illustrate the change in relative angle of the head 6 over time during a golf swing relative to the initial position of the head 6. In the figures, the phases of the golf swing are divided into a backswing (solid line), downswing (dashed line), and follow through (dotted line). The phases of the golf swing can be distinguished by, for example, setting up an image pickup apparatus other than the image pickup apparatus 4 to film the entire golf swing by the golfer 8 or by providing a gyro sensor in the golf club 3. Thus distinguishing the phases of the golf swing allows for a phase-by-phase comparative assessment of the measurement results for different types of golf swings.

As is clear from FIGS. 9A to 9C and FIGS. 10A to 10C, the measurement results for each subject differ mutually. By comparing and categorizing the measurement results after determining characteristics to be compared or features to use as an index, it is thus considered possible to select a golf club appropriate for each subject and to support development.

While an embodiment of the present invention has been described, a variety of modifications may be made without deviating from the scope of the present invention. Note that in the above embodiment, the golfer 8 is indicated as being human, yet according to the present invention, it is also possible easily to measure deformation of the golf club during a golf swing by a robot golfer. Such a robot golfer can execute a swing under fixed conditions and can, for example, easily assess uniformity of characteristics between a plurality of products having the same specifications.

REFERENCE SIGNS LIST

-   1: Measurement system -   2: Measurement apparatus -   3: Golf club -   4: Image pickup apparatus -   5: Shaft -   6: Head -   7: Grip -   9: Golf ball 

1-8. (canceled)
 9. A system for measuring golf club deformation during a swing of a golf club by a golfer, comprising: an image pickup apparatus attached to the golf club and facing a direction that includes at least one identifier attached to the golf club for specification of a position on the golf club; and a measurement apparatus configured to measure the golf club deformation based on position information of the at least one identifier, the position information being acquired from an image of the golf club captured by the image pickup apparatus during the swing.
 10. The system according to claim 9, wherein the measurement apparatus comprises: an image acquisition unit configured to acquire the image of the golf club during the swing from the image pickup apparatus; a position information acquisition unit configured to recognize the at least one identifier in the acquired image and to acquire position information of the recognized at least one identifier; and a measurement unit configured to measure the golf club deformation based on the acquired position information.
 11. The system according to claim 9, wherein the at least one identifier is provided on a head of the golf club.
 12. The system according to claim 9, wherein the golf club deformation is at least one of movement of a head and flex of a shaft of the golf club.
 13. The system according to claim 9, wherein the image pickup apparatus weighs less than 90 g.
 14. The system according to claim 9, wherein the image pickup apparatus is attached immediately below or near a grip of the golf club.
 15. A method for measuring golf club deformation during a swing of a golf club by a golfer, comprising: capturing an image of the golf club with an image pickup apparatus during a golf swing using the golf club, the golf club including at least one identifier for specification of a position on the golf club and having the image pickup apparatus attached thereto facing a direction that includes the at least one identifier; acquiring the image of the golf club during the swing from the image pickup apparatus; recognizing the at least one identifier in the image captured by the image pickup apparatus and acquiring position information of the recognized at least one identifier; and determining the golf club deformation based on the acquired position information.
 16. An apparatus for measuring golf club deformation during a swing of a golf club by a golfer, wherein the apparatus measures the golf club deformation based on position information of at least one identifier attached to the golf club for specification of a position on the golf club, the position information being acquired from an image of the golf club captured during the swing by an image pickup apparatus attached to the golf club and facing a direction that includes the at least one identifier. 